Giganteus Plants Research Articles

Plant Growth-Promoting Endophytic Bacteria Isolated from Miscanthus giganteus and Their Antifungal Activity.

Modern technologies can satisfy human needs only with the use of large quantities of fertilizers and pesticides that are harmful to the environment. For this reason, it is possible to develop new technologies for sustainable agriculture. The process could be carried out by using endophytic microorganisms with a (possible) positive effect on plant vitality. Bacterial endophytes have been reported as plant growth promoters in several kinds of plants under normal and stressful conditions. In this study, isolates of bacterial endophytes from the roots and leaves of Miscanthus giganteus plants were tested for the presence of plant growth-promoting properties and their ability to inhibit pathogens of fungal origin. Selected bacterial isolates were able to solubilize inorganic phosphorus, fix nitrogen, and produce phytohormones, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, and siderophore. Leaf bacterial isolate Pantoea ananat is 50 OL 2 had high production of siderophores (zone ≥ 5 mm), and limited phytohormone production, and was the only one to show ACC deaminase activity. The root bacterial isolate of Pseudomonas libanensis 5 OK 7A showed the best results in phytohormone production (N6-(Δ2-isopentenyl)adenine and indole-3-acetic acid, 11.7 and 12.6 ng·mL-1, respectively). Four fungal cultures-Fusarium sporotrichioides DBM 4330, Sclerotinia sclerotiorum SS-1, Botrytis cinerea DS 90 and Sphaerodes fimicola DS 93-were used to test the antifungal activity of selected bacterial isolates. These fungal cultures represent pathogenic families, especially for crops. All selected root endophyte isolates inhibited the pathogenic growth of all tested fungi with inhibition percentages ranging from 30 to 60%. Antifungal activity was also tested in two forms of immobilization of selected bacterial isolates: one in agar and the other on dextrin-coated cellulose carriers. These results demonstrated that the endophytic Pseudomonas sp. could be used as biofertilizers for crops.

ВИКОРИСТАННЯ БІОЧАРУ І МІСКАНТУСУ ГІГАНТСЬКОГО (MISCANTHUS GIGANTEUS) ДЛЯ РЕМЕДІАЦІЇ ҐРУНТУ, ЗАБРУДНЕНОГО НАФТОПРОДУКТАМИ

The dynamics of changes in the chemical composition of soils contaminated with oil products during the vegetation of Miscanthus giganteus, as well as under the conditions of adding biochar (biochar) were studied. The possibility of using the culture of Miscanthus giant and biochar for soil remediation under conditions of oil pollution was analyzed. It was shown that the introduction of biochar into the soil enriched it with nitrate nitrogen, which was actively assimilated by giant miscanthus plants during the growing season. The absorption of nitrate anions by plants was especially active in the second series of the experiment, when the soil + biochar was contaminated with diesel fuel. It was established that the content of NH4+ ions in both series of the experiment increased until the end of the growing season. Obviously, ammonium nitrogen is absorbed to a lesser extent by M. giganteus plants, compared to nitrate. The increase in ammonium content can be additionally caused by the activity of soil microbes in the rhizosphere of plants, which contributes to the accumulation of ammonium nitrogen in the soil. It has been shown that miscanthus plants actively absorbed water-soluble forms of phosphorus, especially in the period from June to September. The application of biochar was a significant source of phosphorus, although its release into the soil is a rather slow process. It was determined that additional amounts of potassium were added to the soil with biochar, which was actively used by the M. giganteus culture. The minimum amounts of potassium in both series of studies were absorbed by plants of E groups, where the content of diesel fuel in the soil was the highest. The introduction of petroleum products had a minor effect on the value of exchangeable acidity. The addition of biochar contributed to the shift of the acid-base balance in the direction of alkalinity, but after the end of the miscanthus vegetation (September), a decrease in the pH of the saline extract of the soil was noted. It is shown that the most noticeable decrease in the concentration of diesel fuel in the soil was noted under the conditions of adding biochar and after growing miscanthus, which can be effectively used for the remediation of lands contaminated by oil products.

An Attempt to Restore the Fertility of Miscanthus × giganteus

Miscanthus × giganteus is a popular industrial plant with great potential in ecological agriculture. It forms numerous rhizomes that are important in the sequestration of carbon dioxide. The plant can be a source of lignin and cellulose, biomass for renewable energy production, and can be used in small garden architecture, or to strengthen the banks of landslides. Breeding this species is difficult, as it is a sterile allotriploid with 57 chromosomes. The aim of the study was to obtain fertile plants of this species by treating its callus and regenerants with chromosome doubling agents such as colchicine, oryzalin, trifluralin, and caffeine at variable concentrations and durations. Callus cells naturally showed large variations in the number of chromosomes but only euploid cells regenerated plants. Treatment of the regenerants with 1252 µM colchicine for 18 h allowed for obtaining two hexaploid shoots; however, they died before flowering. Colchicine and oryzalin stimulated the formation of mixoploid shoots. The investigated substances, except for caffeine, were highly toxic to plants. M. × giganteus plants with 114 chromosomes may die because such a high number of chromosomes may be unfavorable for cells of this species.

Towards Sustainable Wastewater Treatment: Bioindication as a Technique for Supporting Treatment Efficiency Assessment.

Constructed wetlands (CWs) are a promising alternative for conventional methods of wastewater treatment. However, the biggest challenge in wastewater treatment is the improvement of the technology used so that it is possible to remove micropollutants without additional costs. The impact of wastewater treatment in CWs on toxicity towards Aliivibrio fischeri, Daphnia magna and Lemna minor was investigated. The effects of feeding regime (wastewater fed in five batches per week at a batch volume of 1 L, or twice per week at a batch volume of 2.5 L) and the presence of pharmaceuticals (diclofenac and sulfamethoxazole), as well as the presence of Miscantus giganteus plants in CW columns (twelve of the 24 columns that were planted) were analyzed. A reduction in toxicity was observed in all experimental setups. The effluents from constructed wetlands were classified as moderately toxic (average TU for A. fischeri, D. magna and L. minor was 0.9, 2.5 and 5.5, respectively). The feeding regime of 5 days of feeding/2 days of resting resulted in a positive impact on the ecotoxicological and chemical parameters of wastewater (removal of TOC, N-NH4 and pharmaceuticals). Extended exposure of Miscantus giganteus to the wastewater containing pharmaceuticals resulted in elevated activity of antioxidant enzymes (catalase and superoxide dismutase) in leaf material.

Biomass yield and quality of the Miscanthus × giganteus in northern China

AbstractMiscanthus × giganteus has attracted much attention and occupied a significant niche as a bioenergy crop to meet the world's energy demand and in the fight against climate change. In this study, a field experiment was conducted to evaluate the yield and biomass characteristics of M. × giganteus over a period of three years from 2013 to 2015 in Beijing, China. M. × giganteus plants showed higher tiller density and litter leaf weight in the third year, whereas no significant difference in plant height was observed among the years. In contrast, a larger number of nodes per plant were recorded in the first year. Biomass yield potential was the highest in the third year (42.3 t ha−1). In addition, plant height (r = .594, p = .042), tiller density (r = .854, p < .01), and number of nodes per plant (r = ‐.589, p = .044) were significantly correlated with biomass yield. Contents of cellulose and lignin were higher in stems, while that of hemicellulose and ash were higher in leaves. M. × giganteus biomass may be used for cellulosic ethanol conversion due to high cellulose and hemicellulose contents and low lignin content and for direct combustion and co‐combustion due to high calorific value (18.5 MJ kg−1). To conclude, our findings indicate that M. × giganteus can be cultivated in northern China as an excellent herbaceous bioenergy crop. Rational utilization of the agronomic characteristics would be helpful to screening and breeding bioenergy grass for promoting bioenergy production in China.

Physiological and biochemical characteristic of Miscanthus × giganteus grown in heavy metal – oil sludge co-contaminated soil

The effect of oil sludge and zinc, present in soil both separately and as a mixture on the physiological and biochemical parameters of Miscanthus × giganteus plant was examined in a pot experiment. The opposite effect of pollutants on the accumulation of plant biomass was established: in comparison with uncontaminated control the oil sludge increased, and Zn reduced the root and shoot biomass. Oil sludge had an inhibitory effect on the plant photosynthetic apparatus, which intensified in the presence of Zn. The specific antioxidant response of M. × giganteus to the presence of both pollutants was a marked increase in the activity of superoxide dismutase (mostly owing to oil sludge) and glutathione-S-transferase (mostly owing to zinc) in the shoots. The participation of glutathione-S-transferase in the detoxification of both the organic and the inorganic pollutants was assumed. Zn inhibited the activity of laccase-like oxidase, whereas oil sludge promoted laccase and ascorbate oxidase activities. This finding suggests that these enzymes play a part in the oxidative detoxification of the organic pollutаnt. With both pollutants used jointly, Zn accumulation in the roots increased 6-fold, leading to increase in the efficiency of soil clean-up from the metal. In turn, Zn did not significantly affect the soil clean-up from oil sludge. This study shows for the first time the effect of co-contamination of soil with oil sludge and Zn on the physiological and biochemical characteristics of the bioenergetic plant M. × giganteus. The data obtained are important for understanding the mechanisms of phytoremediation with this plant.

The formation of the leaf surface area and biomass of the miscanthus giganteus plants depending on the sewage sludge rate

The case study to determine the peculiarities of Miscanthus giganteus aboveground biomass formation depending on sewage sludge and composts rate carried out in the Precarpathian region of Ivano- Frankivsk province on sod-podzolic soils. The largest area of the leaf surface of miscanthus is formed in the trials where fresh sewage sludge was applied in the rate of 20 - 40 t/ha. The leaf surface area increases from 19 up to 24.0 cm2/plant, and the yield of raw mass of plants at the level of 23.5 - 25.1 t/ha due to increasing rates of sewage sludge application. The highest indicators of net photosynthesis productivity were found in the period of intensive growth, which amounted to 7.78 g/m²/day and in the maturation period of 7.56 g/m²/day in the trial SS - 40 t/ha + N10P14K58. The amount of dry mass of miscanthus plants significantly depends on the height of the shoot and the leaf surface area of the plants. The use of compost based on sewage sludge and straw in a ratio of 3: 1 at a rate of 30 t/ha contributes to the dry weight of miscanthus plants at the level of 15 t/ha.

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Reproduction and conservation of soil fertility, protection against degradation and pollution is traditionally one of the priority tasks of the state agricultural policy. The presence of petroleum products in soils causes violation of ecological balance in the soil system, changes in morphological and physicochemical characteristics of soil horizons, in the ratio between the individual fractions of soil organic matter. Therefore, today more and more attention is paid to the development and implementation of innovative technologies for purification of oil-contaminated soils. Phytoremediation is currently considered to be the most promising method for сleaning of polluting in industrialized countries. The material elucidates the results of the study of changes in agrochemical parameters of soil in consequence of oil pollution and сarrying out of phytoremediation, determined the dynamics of the degree of purification of oil-contaminated soils, reducing their phytotoxicity by growing bioenergy culture Miscanthus giganteus. The model experiment was conducted in natural conditions of the scientific-research plot of Poltava State Agrarian Academy. Oil was applied to the soil in the following concentrations: 10, 20 and 40 g/kg. Three weeks after the application of oil into the soil, vegetative shoots of Miscanthus giganteus were planted out in the first year of life. The period of oil degradation in the soil lasted 177 days, of which 156 days – the reclamation period with using the bioenergy plant Miscanthus giganteus. It was found that growing Miscanthus giganteus on oil-contaminated soil with the application of 40 g/kg reduced the content of petroleum products by 13% compared to the control variant – without plants. With increasing concentration of oil pollution after phytoremediation of Miscanthus giganteus, the pH of the soil solution and metabolic acidity increases, the amount of absorbed bases decreases, the intensity of respiration increases significantly. The content of organic carbon in the soil was characterized by the following indicеs: at contamination of 10 g/kg the content of organic carbon reached 4.4%, at pollution of 20 g/kg – 6.1%, and at 40 g/kg – 7.0%, respectively, the content of organic matter was 8.3%, 11.5% and 13.2%, the content of humus – 7.59%, 10.52% and 12.07%. Miscanthus giganteus plants create favorable conditions for the development of microorganisms and increase their activity in consequence of the secretion of nutrients by the roots, improving soil properties. Thus, second-regeneration biofuel plants Miscanthus giganteus can be recommended for phytoremediation of oil-contaminated soils and thus, on the one hand, clean large areas of land, and on the other – to obtain biomass for further energy production, which will be environmentally friendly and economically feasible.

The weed pollution in Miscanthus giganteus

Goal. Is to determine the species composition of weeds in Miscanthus giganteus plantings, their impact on biomass productivity and the development of an effective protection system. Methods. Field experiments, laboratory agrochemical studies, mathematical and statistical — to evaluate the reliability of the obtained data. Results. At the beginning of the first year of vegetation in the miscanthus crops, the type of weed was mixed, with a large predominance of annual monocotyledonous species 91.1—93.6%. But in the second (70.1—85.3%) and the third (51.1—79.8%) years of vegetation, dicotyledonous species prevailed, while in the fourth, the monocotyledonous species (55.6—64.8%) had a slight advantage. In the first year of vegetation the weed was quite high and amounted to 1156 p./m2, in the second year — 873 p./m2, it decreased to 380—386 p./ m2. On the variants of application of herbicides for the second and next years, a decrease in the number of weeds by 41.3—64.5% compared with the weed pollution control and depending on the year of vegetation was observed. In the conditions of co-vegetation of weed plants with the weeds, the largest mass was formed by the Chenopodium album L. (930 g/m2 in the first year and 93 g/ m2 in the fourth year), Amaranthus retroflexus L. (455 g/ m2 and 60.6 g/ m2), Artemisia annua L. (280 g/m2 and 29.1 g/m2) and annual monocotyledonous Echinochloa crus-galli (L.) Pal. Beauv. (225 g/ m2 and 17 g/ m2) and Setaria glauca (L.) Pal. Beauv (360 g/ m2 and 15.4 g/ m2). Weed pollution control on miscanthus crops helped to increase the biomass yield in the first year of vegetation to 2.6—2.7 t/ha of wet weight, to the fourth — up to 36.3—37.4 t/ ha. In the Weed pollution control, only 0.5 t/ha were obtained in the first year of vegetation, while in the fourth year it was 22.1 t/ ha. Conclusions. A mixed type of weed was found on the landing of Miscanthus giganteus, with 19 species from 12 families. Application of herbicides Task Extra and Master Power weed pollution reduction by 83.3—99.2%, which made it possible to improve the conditions of growing and development of Miscanthus giganteus plants and to obtain a dry biomass yield of 20.0 t/ha for the fourth year of vegetation.

Enrichment of endophytic Actinobacteria in roots and rhizomes of Miscanthus × giganteus plants exposed to diclofenac and sulfamethoxazole.

This study investigates how wastewater containing 2mgl-1 of sulfamethoxazole (SMX) and 2mgl-1 of diclofenac (DCF) affects the composition of bacterial communities present in the roots and rhizomes of Miscanthus × giganteus plants grown in laboratory-scale constructed wetlands. Bacterial communities in plant roots and rhizomes were identified in treated and control samples by 16S rRNA amplicon sequencing. Moreover, bacterial endophytes were isolated in R2A and 1/10869 media and screened for their ability to metabolize SMX and DCF in liquid medium by HPLC. Our results show significant changes in the abundance of main genera, namely Sphingobium and Streptomyces between control and treated plants. Around 70% of the strains isolated from exposed plants belonged to the phylum Actinobacteria and were classified as Streptomyces, Microbacterium, and Glycomyces. In non-exposed plants, Proteobacteria represented 43.5% to 63.6% of the total. We identified 17 strains able to remove SMX and DCF in vitro. From those, 76% were isolated from exposed plants. Classified mainly as Streptomyces, they showed the highest SMX (33%) and DCF (41%) removal efficiency. These isolates, alone or in combination, might be used as bio-inoculants in constructed wetlands to enhance the phytoremediation of SMX and DCF during wastewater treatment.

Zinc accumulation, photosynthetic gas exchange, and chlorophyll a fluorescence in Zn-stressed Miscanthus × giganteus plants

Accumulation and distribution of zinc within Miscanthus × giganteus plants grown on elevated Zn concentrations and their photosynthetic performance were investigated. High concentrations of Zn in soils caused an increase of its concentrations in all plant organs. The bioconcentration factor, bioaccumulation factor, and translocation factor were lower than one indicating that M. × giganteus is an excluder plant species. Excessive Zn induced visible leaf damage, i.e. chlorosis and necrosis, only in the oldest leaves, pointing to Zn accumulation. Elevated amounts of Zn in leaves significantly lowered the photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentrations, parameters of chlorophyll a fluorescence, and chlorophyll b content. Despite Zn excess in leaves, there was no severe reduction in the maximal quantum yield of PSII photochemistry, indicating a high photosynthetic capacity, high tolerance to elevated Zn concetrations, and ability of M. × giganteus to grow on Zn-contaminated soils.

Description and Codification of Miscanthus × giganteus Growth Stages for Phenological Assessment.

Triploid Miscanthus × giganteus (Greef et Deu. ex Hodkinson et Renvoize) is a sterile, perennial grass used for biomass production in temperate environments. While M. × giganteus has been intensively researched, a scale standardizing description of M. × giganteus morphological stages has not been developed. Here we provide such a scale by adapting the widely-used Biologische Bundesanstalt, Bundessortenamt, CHemische Industrie (BBCH) scale and its corresponding numerical code to describe stages of morphological development in M. × giganteus using observations of the “Freedom” and “Illinois” clone in Iowa, USA. Descriptive keys with images are also presented. Because M. × giganteus plants overlap in the field, the scale was first applied to individual stems and then scaled up to assess plants or communities. Of the 10 principal growth stages in the BBCH system, eight were observed in M. × giganteus. Each principal stage was subdivided into secondary stages to enable a detailed description of developmental progression. While M. × giganteus does not have seed development stages, descriptions of those stages are provided to extend the scale to other Miscanthus genotypes. We present methods to use morphological development data to assess phenology by calculating the onset, duration, and abundance of each developmental stage. This scale has potential to harmonize previously described study-specific scales and standardize results across studies. Use of the precise staging presented here should more tightly constrain estimates of developmental parameters in crop models and increase the efficacy of timing-sensitive crop management practices like pest control and harvest.

BEHAVIOUR OF Miscanthus AT CUTTING SHEAR WITH STRAIGHT KNIVES WITH DIFFERENT EDGE ANGLES

This paper presents some experimental results regarding mechanical behaviour at shear cutting Miscanthus x giganteus stem with an oblique blade of different edge angles. Experimental determinations were performed using samples of about 30 mm in length and a medium diameter of about 6.3 mm to 8.9 mm. The biomass was cut with three bevel cutting blades of 30 degrees, with a tool angle of 10, 30 and 50 degrees, fitted on an equipment used for mechanical experiments type Hounsfield, with a working speed of 500 mm/min. Using QMat program force-deformation graphics for each sample were saved. The results are shown through force-deformation graphics obtained during testing and also shown through geometric parameters influence of stems on the cutting process. The specific cutting force values were between 31 and 34 N/mm, for the bevel cutting angle between 10 and 50 degrees, and the specific cleavage energy between (13.07 -47.07) x103 J/m2, confirming the results in the field. The energy consumption for cutting a hectare of Miscanthus crop is situated between 0.55 - 1.35 MJ/ha, calculated for 75 plants per square meter. Mechanical behaviour of Miscanthus x giganteus plant is necessary to be known for specialists in order to design equipment s with an optimum function process, for dimensioning and projecting harvesting and grinding biomass (Miscanthus) equipment s in order to minimize energy consumption or to grow the working capacity of the machines.

Quantitative Trait Loci (QTL)-Guided Metabolic Engineering of a Complex Trait.

Engineering complex phenotypes for industrial and synthetic biology applications is difficult and often confounds rational design. Bioethanol production from lignocellulosic feedstocks is a complex trait that requires multiple host systems to utilize, detoxify, and metabolize a mixture of sugars and inhibitors present in plant hydrolysates. Here, we demonstrate an integrated approach to discovering and optimizing host factors that impact fitness of Saccharomyces cerevisiae during fermentation of a Miscanthus x giganteus plant hydrolysate. We first used high-resolution Quantitative Trait Loci (QTL) mapping and systematic bulk Reciprocal Hemizygosity Analysis (bRHA) to discover 17 loci that differentiate hydrolysate tolerance between an industrially related (JAY291) and a laboratory (S288C) strain. We then used this data to identify a subset of favorable allelic loci that were most amenable for strain engineering. Guided by this "genetic blueprint", and using a dual-guide Cas9-based method to efficiently perform multikilobase locus replacements, we engineered an S288C-derived strain with superior hydrolysate tolerance than JAY291. Our methods should be generalizable to engineering any complex trait in S. cerevisiae, as well as other organisms.

Plant and soil effects on bacterial communities associated with Miscanthus × giganteus rhizosphere and rhizomes

AbstractBacterial assemblages, especially diazotroph assemblages residing in the rhizomes and the rhizosphere soil of Miscanthus × giganteus, contribute to plant growth and nitrogen use efficiency. However, the composition of these microbial communities has not been adequately explored nor have the potential ecological drivers for these communities been sufficiently studied. This knowledge is needed for understanding and potentially improving M. × giganteus – microbe interactions, and further enhancing sustainability of M. × giganteus production. In this study, cultivated M. × giganteus from four sites in Illinois, Kentucky, Nebraska, and New Jersey were collected to examine the relative influences of soil conditions and plant compartments on assembly of the M. × giganteus‐associated microbiome. Automated ribosomal intergenic spacer (ARISA) and terminal restriction fragment length polymorphism (T‐RFLP) targeting the nifH gene were applied to examine the total bacterial communities and diazotroph assemblages that reside in the rhizomes and the rhizosphere. Distinct microbial assemblages were detected in the endophytic and rhizosphere compartments. Site soil conditions had strong correlation with both total bacterial and diazotroph assemblages, but in different ways. Nitrogen treatments showed no significant effect on the composition of diazotroph assemblages in most sites. Endophytic compartments of different M. × giganteus plants tended to harbor similar microbial communities across all sites, whereas the rhizosphere soil of different plant tended to harbor diverse microbial assemblages that were distinct among sites. These observations offer insight into better understanding of the associative interactions between M. × giganteus and diazotrophs, and how this relationship is influenced by agronomic and edaphic factors.

In vitro-propagated Miscanthus × giganteus plants can be a source of diversity in terms of their chemical composition

Miscanthus × giganteus is a triploid hybrid propagated vegetatively from rhizomes or in a tissue culture, so its clones are characterised by a very low genetic diversity. Giant Miscanthus is cultivated mainly for biomass used as biofuel; depending on its chemical composition, it can be used in many industries. The goal of this work was to determine whether regenerants obtained in tissue culture can be a source of new forms characterised by different biomass yield and energy values as well as by their concentration of cellulose, hemicellulose and lignin. In the study the number and height of stems as well as the dry weight, ash and water mass fraction of biomass were estimated. The study was performed on Miscanthus plants propagated from rhizomes obtained from two different locations in Poland (Zabierzów – Z and Radzików – R), and on regenerants (Iv) obtained from Z plants. The results indicated that somaclonal variation occurs in M. × giganteus cultures and that regenerants show low polymorphic variation compared to donor plants. Plants propagated in an in vitro culture showed the lowest stem height, but the highest number of stems per plant. Dry matter yield was greatest in the R group, while regenerants demonstrated the highest level of hemicellulose fraction and lowest cellulose and lignin concentration. Energy value was the highest for Z plants, but Iv plants showed energy values on the same level as those of R plants. The data suggest that in vitro-propagated plants may be a source of new Miscanthus forms.

Propagation method affects Miscanthus × giganteus developmental morphology

The Illinois clone of Miscanthus×giganteus has many traits of an ideal biomass crop, including sterility, which significantly limits invasive potential. However, this sterility necessitates vegetative propagation, a time and labor intensive process that currently challenges the crop's adoption. Traditionally propagated by rhizome segments, M.×giganteus can also reproduce by stems like its relative, sugarcane. Previous work indicates, however, that non-traditional propagation of M.×giganteus can affect developmental morphology of resultant plants in the field. We investigated the effect of stem propagation on developmental morphology (part I, this paper), and survival and yield (part II), of field-grown M.×giganteus (Illinois clone) plants at three sites in Iowa, USA during the second and third year of growth. Although stem propagation affected morphology compared to traditional rhizome propagation, the differences were less pronounced than reported for hormone-aided micropropagation. Observed differences (and similarities) between stem and rhizome propagated plants were consistent between different growing environments and years, despite extreme weather. Rhizome propagated plants had larger basal circumferences (146.2cm vs. 134.7cm on average, P=0.0107), but stem propagated plants had more stems per plant (38 vs. 33 on average, P=0.0492) suggesting that these two propagation techniques result in plants with different growth strategies but may achieve similar yields. Though small, these differences persisted consistently throughout the duration of this experiment, suggesting morphological differences may be maintained over time in mature stands of M.×giganteus.

Tolerance of Miscanthus × giganteus to salinity depends on initial weight of rhizomes as well as high accumulation of potassium and proline in leaves

Miscanthus×giganteus, a species useful for sustainable agriculture, can be cultivated on soils with lower bonitation and also with higher salinity. The study aimed to estimate NaCl concentrations which limit growth of Miscanthus×giganteus plants and to determine physiological parameters best reflecting the response of Miscanthus to salt stress. The experiment was conducted on plants grown at 0–200mM of NaCl. All analyses were done after 12 weeks of salt treatment. In rhizomes and leaves, fresh (FW) and dry weight (DW), relative water content (RWC), electrolyte leakage (EL), and ion content were determined; in leaves only, chlorophyll fluorescence, net photosynthesis rate (PN), transpiration (E), stomatal conductance (gs) and proline content. Shoots developed at all NaCl concentrations, but at 200mM many rhizomes produced none; thus analyses on leaves were done only on plants grown at 0–150mM of NaCl. Salinity decreased FW and DW of roots and shoots significantly, and retarded increases in rhizome weight. In leaves, salinity of 100 and 150mM NaCl did not damage membrane structures, while in rhizomes only 200mM increased EL considerably. Most parameters of chlorophyll fluorescence and gas exchange declined under salinity. High amounts of proline, K and Na were accumulated in leaves at 100 and 150mM NaCl. RWC remained unchanged in roots and leaves and decreased in rhizomes under rising salinity. The initial FW of the rhizomes studied correlated with the salt tolerance of Miscanthus plants. Changes in chlorophyll fluorescence, PN, FW and DW of roots and leaves as well as potassium and proline concentrations in leaves are the most reliable indicators of the response of Miscanthus to salinity. A high accumulation of K+ and proline in leaves reduces the sodium effect and determines the tolerance of Miscanthus to salinity.

Diversity in ploidy levels and nuclear DNA amounts in Korean Miscanthus species

Because of its high biomass productivity and nutrient-use efficiency, Miscanthus spp. have emerged as promising bioenergy crops. Polyploidism in Miscanthus species is important because it allows non-native countries to cultivate sterile types, such as triploid M. × giganteus, in order to prevent ecosystem disturbance. Although M. sacchariflorus and M. sinensis are considered to be native to Korea, China, and Japan, accurate information describing the ploidy levels of these species has not yet been well established. To evaluate rough ploidy levels, 215 accessions of Miscanthus species were estimated by relative fluorescence intensities of DAPI-stained nuclei. After evaluation of rough ploidy levels, 20 plants were randomly selected by species and ploidy levels, and ploidy levels were examined by counting chromosomes, estimating propidium iodide-stained DNA content with flow cytometry, and measuring sizes of stomata and caryopsis. Among the 20 plants examined, 3 were diploid and 6 were tetraploid M. sacchariflorus (4.56 ± 0.01 and 8.90 ± 0.14 pg/2C nuclear DNA content, respectively), while 6 were diploid and 3 were triploid M. sinensis (5.40 ± 0.18 and 8.29 ± 0.33 pg/2C nuclear DNA content, respectively). One plant was a putative triploid M. × giganteus having 7.31 pg/2C nuclear DNA content, which was similar to an M. × giganteus plant from Illinois, USA having 7.23 pg/2C nuclear DNA content. We confirmed the occurrence of diploid and tetraploid M. sacchariflorus and M. sinensis plants as well as a putative triploid M. × giganteus native to Korea. Thus, measurement of the size of stomata and caryopsis allowed prediction of ploidy levels in the field and laboratory.

Mass and compositional changes, relevant to biorefining, in Miscanthus x giganteus plants over the harvest window

Miscanthus plants were sampled from several plantations in Ireland over the harvest window (October-April). These were separated into their anatomical components and the loss of leaves monitored. Three distinct phases were apparent: there was minimal loss in the "Early" (October to early December) and "Late" (March and April) phases, and rapid leaf loss in the interim period. Samples were analysed for constituents relevant to biorefining. Changes in whole-plant composition included increases in glucose and Klason lignin contents and decreases in ash and arabinose contents. These changes arose mostly from the loss of leaves, but there were some changes over time within the harvestable plant components. Although leaves yield less biofuel than stems, the added biomass provided by an early harvest (31.9-38.4%) meant that per hectare biofuel yields were significantly greater (up to 29.3%) than in a late harvest. These yields greatly exceed those from first generation feedstocks.